Electronic amusement games have been made which use a digital computer to control a visible display, and which "play" a game in accordance with a game program stored in a read only memory. It is common to provide the game programs in the form of cartridges which have electrical connectors that may be readily plugged into the game computer. The cartridges contain read only memory devices which store game programs. This allows the same game computer to be used for a large number of different games. The game program for the game computer may be changed by un-plugging one cartridge (the old game) and plugging in a different cartridge (the new game). It is common to sell game cartridges separately from a game computer so that the buyer may choose which games he or she wants to play and may buy only the cartridges he or she desires. This also allows the buyer to purchase additional cartridges after buying a game computer, so that the buyer may add to his selection of games. The use of cartridges also allows the manufacturer of electronic games to develop new games after introducing a game computer. For example, a supplier of video games for home use may begin producing cartridges for a game which has proven popular on coin-operated video game machines which are used in public arcades.
A problem for a manufacturer of cartridge-type video games is that it is relatively easy for unscrupulous competitors to produce unauthorized copies of cartridges. Extremely valuable game programming may be misappropriated by copying the stored program into counterfeit cartridges which may be fabricated using commonly available electronic components. The distribution of such unauthorized game program copies injures the game computer manufacturer and discourages the release of popular games on cartridges.
Another problem for a manufacturer of cartridge-type video games is that the design of a game computer and its cartridge electrical connector may place limitations on the size of a game program which may be placed in a cartridge. For example, the number of electrical conductors passing through the cartridge connector may limit the number of program addresses which are sent from the game computer to the cartridge. This limitation on addressing presents limitations on the length of game programs which may be placed in a cartridge. As the types of video games become more sophisticated and complex, the required program length increases. It may be very difficult to place new, challenging, intricate games into conventionally constructed game cartridges with program length constraints.